Single crystal gas turbine engine components offer the promise of improved performance in gas turbine engines. U.S. Pat. No. 3,494,709 which is assigned to the assignee of the present invention, discloses the use of single crystal components in gas turbine engines. This patent discusses the desirability of limiting certain elements such as boron and zirconium to low levels. The limitation of carbon to low levels in single crystal superalloy articles is discussed in U.S. Pat. No. 3,567,526. U.S. Pat. No. 4,116,723 describes heat treated superalloy single crystal articles which are free from intentional additions of cobalt, boron, zirconium and hafnium. According to this patent, elimination of these elements render the compositions heat treatable.